The invention relates to a jetting head capable of ejecting various kinds of liquid in the form of droplets for use in an ink jet printer, a display manufacturing apparatus, an electrode forming apparatus, a biochip manufacturing apparatus, etc., and more particularly, to a jetting apparatus having a plurality of flexible flat cables to be used for supplying drive signals from a head driver to a jetting head.
As a jetting apparatus having a jetting head capable of ejecting liquid in the form of a liquid droplet, for example, there has been proposed an ink jet printer in which ink droplets are ejected to record an image or the like on recording paper, an electrode forming apparatus in which an electrode material in a liquid form is ejected onto a substrate to thereby form electrodes, a biochip manufacturing apparatus in which biological samples are ejected to manufacture biochips, or a micropipette for ejecting a predetermined amount of a sample into a vessel.
For instance, in an ink jet printer employing piezoelectric elements as drive elements for ejecting ink, a plurality of piezoelectric elements, which are provided so as to correspond to a plurality of nozzles of a print head, are selectively activated, whereby ink droplets are ejected from the nozzles in accordance with the dynamic pressure generated by the respective piezoelectric elements. Dots are formed on recording paper by causing the ink droplets to adhere to the recording paper, thus effecting printing operation.
Here, the piezoelectric elements are provided so as to correspond to nozzles to be used for ejecting ink droplets. The piezoelectric elements are actuated by a drive signal supplied from a head driver mounted in the print head, thereby ejecting ink droplets.
Drive signals output from the head driver are sent to a print head by way of a flexible flat cable.
More specifically, as shown in FIG. 6, a drive signal COM output from a head driver 1 is divided for respective rows of color nozzles. In relation to a row of nozzles A (hereinafter simply called a “nozzle row A” or “row A”), the head driver 1 outputs, to the print head and over a flexible flat cable, a drive signal COMA and a ground signal AGNDA serving as a return signal for the drive signal COMA. In relation to a row of nozzles B (hereinafter simply called a “nozzle row B” or “row B”), the head driver 1 outputs, to the print head and over the flexible flat cable, a drive signal COMB and a ground signal AGNDB serving as a return signal for the drive signal COMB. In relation to a row of nozzles C (hereinafter simply called a “nozzle row C” or “row C”), the head driver 1 outputs, to the print head and over the flexible flat cable, a drive signal COMC and a ground signal AGNDC serving as a return signal for the drive signal COMC (a signal in which the same current flows in a direction opposite to the drive signal). In relation to a row of nozzles D (hereinafter simply called a “nozzle row D” or “row D”), the head driver 1 outputs, to the print head and over the flexible flat cable, a drive signal COMD and a ground signal AGNDD serving as a return signal for the drive signal COMD.
Here, the drive signals COMA, COMB, COMC, COMD, and the ground signals AGNDA, AGNDB, AGNDC, AGNDD assume the form of a relatively large electric current. For instance, as shown in FIG. 8, each of signal lines corresponding to the respective signals is split into a plurality of signal lines; e.g., two signal lines. The drive signal and the ground signal are connected in parallel to each other by way of the thus-split signal lines. In view of the number of signal lines provided in a flexible flat cable, two flexible flat cables FFC1, FFC2 are used, as shown in FIG. 7.
In connection with the nozzle rows A, B, C, and D assigned to respective colors of the print head, as shown in FIG. 8, the drive and ground signals are allocated, on a per-row basis, to the signal lines of the respective flexible flat cables FFC1, FFC2. Specifically, the drive signal COMA for the nozzle row A and the ground signal AGNDA serving as a return signal for the drive signal COMA are allocated to signal lines such that the drive signal and the ground signal are arranged alternately. The drive signal COMB and the ground signal AGNDB serving as a return signal for the drive signal COMB are allocated to signal lines in the same manner. The drive signal COMC and the ground signal AGNDC serving as a return signal for the drive signal COMC are allocated to signal lines in the same manner. Further, the drive signal COMD and the ground signal AGNDD serving as a return signal for the drive signal COMD are allocated to signal lines in the same manner.
As shown in FIG. 7, the flexible flat cables FFC1, FFC2 are set within the printer main unit while remaining superimposed.
In an ink jet printer having the flexible flat cables FFC1, FFC2 of such a configuration, the head driver sends a drive signal and a corresponding ground signal to the print head on a per-color-row basis over the signal lines of the respective flexible flat cables FFC1, FFC2. As a result, piezoelectric elements provided in the print head are driven by the drive signal, and nozzles associated with the piezoelectric elements eject ink droplets, thus effecting printing operation.
In this case, the drive signal lines and the ground signal lines are allocated on a per-row basis. In particular, the nozzle rows A and B and the nozzle rows C and D are thoroughly separated from each other. Eventually, crosstalk developing between the drive and ground signals of the nozzle rows A, B and those of the nozzle rows C, D is reduced, thereby inhibiting occurrence of interference, which would otherwise arise between respective nozzle rows.
Consequently, when the nozzle row A is brought into, e.g., a total ON or OFF condition, there does not occur changes in waveforms of signals flowing through signal lines for the nozzle row B located adjacent to signal lines for the nozzle row A within the flexible flat cables FFC1, FFC2.
However, in the flexible flat cables FFC1, FFC2 having such a configuration, the signal lines of the flexible flat cable FFC1 are located adjacent to and oppose those of the flexible flat cable FFC2.
Therefore, in relation to combinations of signal lines in which the signal lines of the flexible flat cable FFC1 and those of the flexible flat cable FFC2 oppose each other; for instance, a combination of signal lines for the row A and those for the row C and a combination of signal lines for the row B and those for the row D illustrated in the drawings, mutually-opposing signal lines are located close to each other. Hence, crosstalk arises between the mutually-opposing signal lines for the rows, thereby inducing occurrence of interference between the rows (hereinafter, this phenomenon will be called “inter-row interference”).
Accordingly, if an attempt is made to effect printing operation in cyan ink C by use of the row C during the course of printing operation being performed in yellow ink Y by use of the row A, the drive and ground signals allocated to the row C affect the drive and ground signals allocated to the row A, for reasons of inter-row interference, thereby disturbing waveforms of the drive and ground signals. As a result, minute changes develop in, e.g., the quantity of yellow ink Y to be ejected by the nozzle A. In particular, such minute changes appear in the form of a line on a printed image on recording paper at the time of printing of minute dots, thereby deteriorating print quality.